Polishing composition and polishing method

ABSTRACT

A polishing composition of the present invention contains silicon dioxide, an acid, and water. Silicon dioxide is, for example, colloidal silica, fumed silica, or precipitated silica. The acid is, for example, hydrochloric acid, phosphoric acid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, boric acid, acetic acid, itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid, glycolic acid, malonic acid, methanesulfonic acid, formic acid, malic acid, gluconic acid, alanine, glycin, lactic acid, hydroxyethylidene diphosphonic acid, nitrilotris(methylene phosphonic acid), or phosphonobutane tricarboxylic acid. The pH of the polishing composition is preferably in the range of 0.5 to 6. The polishing composition can be suitably used in applications for polishing a glass substrate.

BACKGROUND OF THE INVENTION

The present invention relates to a polishing composition for use inpolishing of a glass substrate for an information-recording medium,which is used for a hard disk and the like. The present invention alsorelates to a polishing method using such a polishing composition.

Conventionally, there is a known polishing composition for use inapplications for polishing a glass substrate for aninformation-recording medium. Japanese Laid-Open Patent Publication No.2001-89748 discloses a polishing composition (hereinafter referred to asthe first prior art polishing composition) containing an abrasive mainlycomposed of a rare earth oxide such as cerium oxide, and water. JapaneseLaid-Open Patent Publication No. 2000-144112 discloses a polishingcomposition (hereinafter referred to as the second prior art polishingcomposition) containing an abrasive that comprises at least one selectedfrom the group consisting of an iron-containing oxide and aniron-containing basic compound, and water. These first and second priorart polishing compositions mechanically polish a glass substrate by theaction of the abrasive.

Requirements to be met by a polishing composition for use inapplications for polishing a glass substrate include:

(1) the surface roughness of the polished glass substrate must be small;

(2) the polishing composition is easy to clean off, namely, thepolishing composition is easily removed by cleaning from the glasssubstrate;

(3) the abrasive has good dispersibility in the polishing composition;and

(4) the polishing composition has a high stock removal rate, i.e., thepolishing composition is highly capable of polishing a glass substrate.

The first and second prior art polishing compositions, however, do notsatisfy the above requirements, and are thus susceptible to improvement.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide apolishing composition that can be suitably used in applications forpolishing a glass substrate. Another object of the present invention isto provide a polishing method using such a polishing composition.

To achieve the foregoing and other objectives and in accordance with thepurpose of the present invention, a polishing composition is provided.The polishing composition, for use in applications for polishing a glasssubstrate, contains silicon dioxide, an acid, and water.

The present invention also provides a method for polishing a glasssubstrate. The method includes preparing the above polishing compositionand polishing the surface of a glass substrate, using the preparedpolishing composition.

Other aspects and advantages of the invention will become apparent fromthe following description, illustrating by way of example the principlesof the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described.

A glass substrate for an information-recording medium, such as amagnetic disc, is formed of, for example, aluminosilicate glass, sodalime glass, soda aluminosilicate glass, almino borosilicate glass,borosilicate glass, quartz glass, or crystallized glass. The maincrystal phase of the crystallized glass may be spodumene, mullite,aluminum borate crystal, β-quartz solid solution, α-quartz, cordierite,enstatite, celsian, wollastonite, anorthite, forsterite, lithiummetasilicate, or lithium disilicate. A glass substrate is usuallyprovided to a chemical machine polishing (CMP) process so as to have thesurface thereof mirror-finished.

Typically, the process of polishing a glass substrate is divided into aplurality of polishing steps to be conducted, for the purpose ofimproving the stock removal rate, as well as the quality of the surfaceof the polished glass substrate. The plurality of polishing stepsinclude, for example, a step of roughly polishing the glass substratesurface and a step of superfinely polishing the glass substrate surface.In other words, the plurality of polishing steps include, for example, astep of preliminarily polishing the glass substrate surface and a stepof finish-polishing the glass substrate surface. A polishing compositionaccording the present embodiment is used, for example, in the finalpolishing step (finish-polishing step) among the plurality of polishingsteps. The polished glass substrate is usually subjected to a chemicalstrengthening process using a low-temperature ion exchange method or thelike, in order to improve resistance to shock and vibration.

The polishing composition according to the present embodiment containssilicon dioxide, an acid, and water.

Silicon dioxide serves as an abrasive for mechanically polishing a glasssubstrate. Silicon dioxide may be colloidal silica, fumed silica, orprecipitated silica. Among them, colloidal silica or fumed silica ispreferable as being capable of reducing the surface roughness of apolished glass substrate, and colloidal silica is more preferable. Oneor more kinds of silicon dioxide may be contained in the polishingcomposition.

When silicon dioxide is colloidal silica, the mean particle diameterD_(SA) of colloidal silica, which is determined from the specificsurface area thereof by the BET method, is preferably in the range of 5to 300 nm, more preferably in the range of 5 to 200 nm, and mostpreferably in the range of 5 to 120 nm. The mean particle diameterD_(N4) of colloidal silica, which is determined by the laser diffractionscattering method, is preferably in the range of 5 to 300 nm, morepreferably in the range of 5 to 200 nm, and most preferably in the rangeof 5 to 150 nm. When silicon dioxide is fumed silica, the mean particlediameter DSA of fumed silica is preferably in the range of 10 to 300 nm,more preferably in the range of 10 to 200 nm, and most preferably in therange of 10 to 120 nm. The mean particle diameter D_(N4) of fumed silicais preferably in the range of 30 to 500 nm, more preferably in the rangeof 40 to 400 nm, and most preferably in the range of 50 to 300 nm. Whenthe mean particle diameter D_(SA) or D_(N4) of colloidal silica is toosmall, or when the mean particle diameter DSA or D_(N4) of fumed silicais too small, it is highly possible that a sufficiently high stockremoval rate will not be obtained. When the mean particle diameterD_(SA) or D_(N4) of colloidal silica is too large, or when the meanparticle diameter DSA or D_(N4) of fumed silica is too large, it ishighly possible that the surface roughness of the polished glasssubstrate will become large, or scratching will occur on the surface ofthe polished glass substrate.

The content of silicon dioxide in the polishing composition ispreferably in the range of 0.1 to 50 mass %, more preferably in therange of 1 to 40 mass %, and most preferably in the range of 3 to 30mass %. When the content of silicon dioxide is less than 0.1 mass %, asufficiently high stock removal rate might not be obtained, or polishingthe glass substrate may become difficult due to high polishingresistance. When the content of silicon dioxide exceeds 50 mass %, theviscosity of the polishing composition excessively increases to make thepolishing composition apt to gelate, leading to reduction inhandleability of the polishing composition.

The acid serves as a polishing accelerator for accelerating mechanicalpolishing by silicon dioxide. The reason why the acid acceleratesmechanical polishing is presumably that the acid acts on the surface ofsilicon dioxide for activation, thereby increasing the mechanicalpolishing force of silicon dioxide. The acid also corrodes or etches theglass substrate surface, as a secondary action, to chemically polish theglass substrate surface. The chemical polishing action of the acid isweaker than the mechanical polishing action of silicon dioxide. The acidmay be an inorganic acid or an organic acid.

Examples of the inorganic acid may include hydrochloric acid, phosphoricacid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, andboric acid. Examples of the organic acid may include acetic acid,itaconic acid, succinic acid, tartaric acid, citric acid, maleic acid,glycolic acid, malonic acid, methanesulfonic acid, formic acid, malicacid, gluconic acid, alanine, glycin, lactic acid, hydroxyethylidenediphosphonic acid (abbreviation: HEDP), nitrilotris(methylene phosphonicacid) (abbreviation: NTMP), and phosphonobutane tricarboxylic acid(abbreviation: PBTC). Among them, hydrochloric acid, phosphoric acid,sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, aceticacid, itaconic acid, succinic acid, tartaric acid, citric acid, maleicacid, glycolic acid, malonic acid, methanesulfonic acid, formic acid,malic acid, gluconic acid, lactic acid, HEDP, NTMP, or PBTC ispreferable, since these acids strongly act to accelerate mechanicalpolishing by silicon dioxide. Among these preferable acids, hydrochloricacid, phosphoric acid, phosphonic acid, tartaric acid, citric acid,maleic acid, or malonic acid is more preferable. One or more acids maybe contained in the polishing composition.

The content of the acid in the polishing composition is preferably inthe range of 0.05 to 10 masse, more preferably in the range of 0.1 to 8mass %, and most preferably in the range of 0.3 to 5 mass %. When thecontent of the acid is less than 0.05 mass %, it is highly possible thata sufficiently high stock removal rate will not be obtained because theacid weakly acts to accelerate mechanical polishing by silicon dioxide.When the content of the acid exceeds 10 mass %, the viscosity of thepolishing composition excessively increases to make the polishingcomposition apt to gelate, which is uneconomical and further increasesthe possibility of producing roughness on the surface of the polishedglass substrate.

Water serves to dissolve or disperse ingredients other than water of thepolishing composition. Water preferably contains as little impurities aspossible so as to avoid inhibiting the actions of other ingredients.Specifically, pure water or ultrapure water, obtained by removingimpurity ions with an ion-exchange resin and then contaminants through afilter, or distilled water, is preferable.

The polishing composition may further contain a chelating agent, asurfactant, a preservative, or the like according to need.

The polishing composition is prepared by mixing ingredients, other thanwater, with water. In the mixing, a blade-type agitator or an ultrasonicdisperser may be used. There is no limitation to the order of mixing theingredients, other than water, into water.

The pH of the polishing composition is preferably not more than 9, morepreferably in the range of 0.5 to 6, further more preferably in therange of 1 to 4, and most preferably in the range of 1 to 2.5. When thepH is higher than 9, it is highly possible that a sufficiently highstock removal rate will not be obtained. When the pH is lower than 0.5,it is highly possible that the handleability of the polishingcomposition will deteriorate. When the pH of the polishing compositionis set to the range of 0.5 to 6, the polishing composition is highlycapable of polishing a glass substrate, thereby to improve the stockremoval rate. The pH of the polishing composition is adjustable bychanging the content of the acid.

A polishing composition according to the present embodiment may beprovided for use after dilution with water, or without dilution. Whenthe polishing composition is diluted with water, the dilution ratio(ratio by volume) is preferably not more than 50 times, more preferablynot more than 20 times, and most preferably not more than 10 times. Whenthe dilution rate exceeds 50 times, the content of silicon dioxide andthe acid in the polishing composition after dilution might becomeexcessively low, resulting in failure to obtain a sufficiently highstock removal rate.

The case where a glass substrate is polished by conducting the two-stagepolishing process consisting of the rough polishing step and thesuperfine polishing step will be described. First, in the roughpolishing step, the surface of a glass substrate is relatively roughlypolished using polishing slurry containing cerium oxide. Next, in thesuperfine polishing step as the final polishing step, the glasssubstrate surface is superfinely polished using the polishingcomposition according to the present embodiment. In the superfinepolishing, in a state where the glass substrate attached to a polishinghead is kept pressed to a polishing pad on a turntable at constantpressure, the polishing composition is provided to the surface of thepolishing pad while the polishing head and the turntable are rotated.

It is to be noted that a glass substrate may be polished in asingle-staged polishing process using a polishing composition accordingto the present embodiment, in place of a multi-stage polishing process.

The present embodiment has the following advantages.

A polishing composition according to the present embodiment containssilicon dioxide as an abrasive. This reduces the surface roughness ofthe polished glass substrate, as compared to a polishing compositioncontaining cerium oxide as an abrasive. Presumably, this is attributedto the fact that the primary particle of cerium oxide has an irregularform whereas the primary particle of silicon dioxide has a sphericalform. Namely, it is presumed that, with the primary particle inspherical form, silicon dioxide is capable of polishing the glasssubstrate surface more finely than cerium oxide, thereby to reducesurface roughness of the polished glass substrate.

Moreover, silicon dioxide has lower reactivity to a glass substratematerial than cerium oxide. For this reason, silicon dioxide attached tothe glass substrate is readily removed by cleaning from the glasssubstrate without reacting with a glass substrate material and stickingto the glass substrate surface. It can therefore be said that apolishing composition according to the present embodiment has theproperty of being readily cleaned off from the polishing surface.

Furthermore, silicon dioxide has greater resistance to agglomeration andhigher dispersibility in the polishing composition than cerium oxide(cf. later-described Examples 1 to 37 and Comparative Examples 4, 5). Itcan therefore be said that a polishing composition according to thepresent embodiment also contains an adhesive having good dispersibility.

The acid in the polishing composition acts to accelerate mechanicalpolishing by silicon dioxide as well as to chemically polish the glasssubstrate surface. By such actions of the acid, the ability of thepolishing composition to polish the glass substrate improves, whichleads to improvement in stock removal rate. It should be noted that,while the acid contributes to improvement in stock removal rate by meansof activation of the silicon dioxide surface and etching of the glasssubstrate surface, it is not considered to act to oxidize the glasssubstrate surface to be made brittle.

Next, examples and comparative examples of the present invention will bedescribed.

An abrasive and a polishing accelerator were mixed with water to preparepolishing compositions according to Examples 1 to 37 and ComparativeExamples 1 to 5. The kinds of abrasives and polishing accelerators usedare as shown in Table 1. The pH of each of the prepared polishingcompositions according to Examples 1 to 37 and Comparative Examples 1 to5 was measured, and the measurement results are shown in Table 1.

The surface of a glass substrate was polished using each of thepolishing compositions according to Examples 1 to 37 and ComparativeExamples 1 to 5 under the polishing conditions described below. Herein,the mass of each glass substrate before and after polishing wasmeasured, and a stock removal rate was then calculated by thebelow-mentioned formula. Based on the obtained stock removal rate, eachof the polishing compositions was rated on a scale from one to four: (1)Very Good; (2) Good; (3) Slightly Poor; and (4) Poor. Specifically, thepolishing composition was rated very good when the stock removal ratewas not less than 0.12 μm/minute; it was rated good when the stockremoval rate was not less than 0.08 μm/minute and less than 0.12μm/minute; it was rated slightly poor when the stock removal rate wasnot less than 0.05 μm/minute and less than 0.08 μm/minute; it was ratedpoor when the stock removal rate was less than 0.05 μm/minute. Theserating results are shown in the column entitled “Stock removal rate” inTable 1.

<Polishing Condition>

Polishing machine: single-sided polishing machine 15″φ (3 pieces/plate),manufactured by Engis Corporation (Japan).

Material to be polished: 2.5-inch (external diameter: 63.5 mm) glasssubstrate obtained by roughly polishing the surface of reinforced glass,using polishing slurry containing cerium oxide, so as to have a surfaceroughness Ra of 0.8 nm.

Polishing pad: Suede type polishing pad “Belatrix N0058,” manufacturedby Kanebo, Ltd.

Polishing pressure: 100 g/cm² (=9.8 kPa)

Turntable rotation speed: 102 rpm

Polishing composition supplied speed: 50 ml/minute

Polishing time: 20 minutes

<Calculation formula>Stock removal rate [μm/minute]=(Difference in mass [g] of glasssubstrate before/after polishing÷(30.02625 [cm²]×2.52 [g/cm³])×10000[μm/cm])÷polishing time [minute]

The polished glass substrate was subjected to scrub cleaning for 30seconds and megasonic cleaning for 45 seconds, and then spin drying for180 seconds. Thereafter, the surface condition of the glass substratewas observed with an atomic force microscope “NanoScope IIIa Dimension3000” (scan area: 10 μm×10 μm, scan rate: 1.00 Hz, sample lines: 256),manufactured by Digital Instruments Inc. Based on the observed number ofadherents to the glass substrate surface, each of the polishingcompositions was rated on a scale from one to four: (1) Very Good; (2)Good; (3) Slightly Poor; and (4) Poor. Specifically, the polishingcomposition was rated very good when the observed number of adherents tothe glass substrate surface was zero; it was rated good when the numberof adherents was less than 3; it was rated slightly poor when the numberof adherents was not less than 3 and less than 5; it was rated poor whenthe number of adherents was not less than 5. These rating results areshown in the column entitled “Ease of cleaning” column in Table 1.

The surface roughness Ra of the glass substrate after spin drying wasmeasured with an atomic force microscope “NanoScope IIIa Dimension 3000”(scan area: 10 μm×10 μm, scan rate: 1.00 Hz, sample lines: 256, off-linefilter: flatten auto order-2). Based on the measured surface roughnessRa of the glass substrate, each of the polishing compositions was ratedon a scale from one to four: (1) Very Good; (2) Good; (3) Slightly Poor;and (4) Poor. Specifically, the polishing composition was rated verygood when the surface roughness Ra was less than 0.2 nm; it was ratedgood when the surface roughness Ra was not less than 0.2 nm and lessthan 0.25 nm: it was rated slightly poor when the surface roughness wasnot less than 0.25 nm and less than 0.3 nm; it was rated poor when thesurface roughness Ra was not less than 0.3 nm. These rating results areshown in the column entitled “Surface roughness” in Table 1.

Each of the polishing compositions according to Examples 1 to 37 andComparative Examples 1 to 5 was put into a calorimetric tube having aninner diameter of 2.5 cm, and allowed to stand there for one hour.Thereafter, the height of a deposit produced in the polishingcomposition in each calorimetric tube was measured. Based on themeasured height of the deposit, each of the polishing compositions wasrated on a scale from one to four: (1) Very Good; (2) Good; (3) SlightlyPoor; and (4) Poor. Specifically, the polishing composition was ratedvery good when the height of the deposit was less than 1 cm; it wasrated good when the height of the deposit was not less than 1 cm andless than 2 cm: it was rated slightly poor when the height of thedeposit was not less than 2 cm and less than 3 cm; it was rated poorwhen the height of the deposit was not less than 3 cm. Those ratingresults are shown in the column entitled “Dispersibility” in Table 1.

Based on the above results of the ratings for the four items: Stockremoval rate, Ease of cleaning, Surface roughness, and Dispersibility,each of the polishing compositions was comprehensively rated on a scalefrom one to four: (1) Very Good; (2) Good; (3) Slightly Poor; and (4)Poor. Specifically, 5 points, 3 points, 1 point and 0 point were givenfor Very Good, Good, Slightly Poor and Poor, respectively, and the totalrating points obtained by each polishing composition was accordinglycalculated. A polishing composition was rated very good when the totalrating points for the four items was 20, it was rated good when thetotal rating points was 16 to 19, it was rated slightly poor when thetotal rating points was 10 to 15, and it was rated poor when the totalrating points was 9 or less. These rating results are shown in thecolumn entitled “Comprehensive rating” in Table 1. TABLE 1 PolishingStock Abrasive accelerator removal Ease of Surface Comprehensive [masspercentage] [mass percentage] pH rate cleaning roughness Dispersibilityrating Ex. 1 colloidal silica maleic acid 1.3 1 1 1 1 1 20% 3% Ex. 2colloidal silica maleic acid 1.6 1 1 1 1 1 20% 1% Ex. 3 colloidal silicamaleic acid 2.2 1 1 1 1 1 20% 0.1% Ex. 4 colloidal silica maleic acid5.0 2 1 1 1 2 20% 0.04% Ex. 5 colloidal silica maleic acid 8.5 3 1 1 1 220% 0.01% Ex. 6 colloidal silica maleic acid 1.5 1 1 1 1 1 10% 1% Ex. 7colloidal silica maleic acid 1.4 3 1 1 1 2 1% 1% Ex. 8 fumed silicamaleic acid 1.7 1 1 3 1 2 20% 1% Ex. 9 colloidal silica maleic acid 2.61 1 1 1 1 40% 1% Ex. 10 colloidal silica phosphoric acid 1.6 1 1 1 1 120% 3% Ex. 11 colloidal silica phosphoric acid 1.9 1 1 1 1 1 20% 1% Ex.12 colloidal silica phosphoric acid 2.5 1 1 1 1 1 20% 0.1% Ex. 13colloidal silica phosphoric acid 9.0 3 1 1 1 2 20% 0.01% Ex. 14colloidal silica phosphoric acid 1.7 2 1 1 1 2 10% 1% Ex. 15 colloidalsilica phosphoric acid 1.7 3 1 1 1 2 1% 1% Ex. 16 fumed silicaphosphoric acid 1.9 1 1 3 1 2 20% 1% Ex. 17 colloidal silica phosphoricacid 2.8 1 1 1 1 1 40% 1% Ex. 18 colloidal silica methanesulfonic acid1.1 1 1 1 1 1 20% 1% Ex. 19 colloidal silica HEDP 1.4 1 1 1 1 1 20% 1%Ex. 20 colloidal silica NTMP 1.4 1 1 1 1 1 20% 1% Ex. 21 colloidalsilica hydrochloric acid 1.4 1 1 1 1 1 20% 1% Ex. 22 colloidal silicaPBTC 1.5 1 1 1 1 1 20% 1% Ex. 23 colloidal silica maleic acid 1.5 1 1 11 1 20% 1% Ex. 24 colloidal silica phosphinic acid 1.7 1 1 1 1 1 20% 1%Ex. 25 colloidal silica tartaric acid 2.1 1 1 1 1 1 20% 1% Ex. 26colloidal silica malonic acid 2.2 1 1 1 1 1 20% 1% Ex. 27 colloidalsilica citric acid 2.4 1 1 1 1 1 20% 1% Ex. 28 colloidal silica malicacid 2.4 1 1 1 1 1 20% 1% Ex. 29 colloidal silica formic acid 2.6 1 1 11 1 20% 1% Ex. 30 colloidal silica glycolic acid 2.8 1 1 1 1 1 20% 1%Ex. 31 colloidal silica itaconic acid 2.9 1 1 1 1 1 20% 1% Ex. 32colloidal silica gluconic acid 2.9 1 1 1 1 1 20% 1% Ex. 33 colloidalsilica succinic acid 3.2 1 1 1 1 1 20% 1% Ex. 34 colloidal silica aceticacid 3.8 2 1 1 1 2 20% 1% Ex. 35 colloidal silica boric acid 7.8 2 1 1 12 20% 1% Ex. 36 colloidal silica alanine 8.6 2 1 1 1 2 20% 1% Ex. 37colloidal silica glycin 8.6 2 1 1 1 2 20% 1% C. Ex. 1 colloidal silica —10.3 4 1 1 1 3 20% C. Ex. 2 colloidal silica aluminum nitrate 3.4 4 1 11 3 25% 1% C. Ex. 3 colloidal silica ammonium molybdate 5.4 4 1 1 1 320% 1% C. Ex. 4 cerium oxide — 6.9 1 4 3 4 4 25% C. Ex. 5 iron oxide —6.9 2 3 3 4 4 25%

In the “Abrasive” column in Table 1:

“Colloidal silica” is colloidal silica having a mean particle sizeD_(SA) of 80 nm and a mean particle size D_(N4) of 80 nm;

“Fumed silica” is fumed silica having a mean particle size D_(SA) of 30nm and a mean particle size D_(N4) of 90 nm;

“Cerium oxide” is cerium oxide (Ce₂O₃) having a mean particle size D₅₀of 450 nm; and

“Iron oxide” is iron oxide (α-Fe₂O₃) having a mean particle diameter D₅₀of 450 nm.

The mean particle diameters D₅₀ of cerium oxide and iron oxide weremeasured using a Coulter counter “LS-230”, manufactured by BeckmanCoulter Inc.

As shown in Table 1, each of the polishing compositions according toExamples 1 to 37 was not rated as poor for any rating item, and wasrated as either very good or good for the “Comprehensive rating”. Thisresult suggests that the polishing compositions according to Examples 1to 37 are useful in applications for polishing a glass substrate. It wasfound from the rating results of the polishing compositions according toExamples 2, 6, 7 and 9 that, when the acid (polishing accelerator) ismaleic acid, an organic acid, the stock removal rate improves, inparticular, by setting the content of silicon dioxide (abrasive) to notless than 10 mass %, and more specifically in the range of 10 to 40 mass%. It was also found from the rating results of the polishingcompositions according to Examples 11, 14, 15 and 17 that, when the acidis phosphoric acid, an inorganic acid, the stock removal rate improves,in particular, by setting the content of silicon dioxide to not lessthan 20 mass %, and more specifically in the range of 20 to 40 mass %.It was further found from the rating results of the polishingcompositions according to Examples 1 to 5 and 10 to 13 that the stockremoval rate improves, in particular, by setting the content of the acidto not less than 0.1 mass %, and more specifically in the range of 0.1to 3 mass %.

The present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. The methodaccording to claim 17, wherein the acid is hydrochloric acid, phosphoricacid, sulfuric acid, phosphonic acid, nitric acid, phosphinic acid, orboric acid.
 11. The method according to claim 17, wherein the acid isacetic acid, itaconic acid, succinic acid, tartaric acid, citric acid,maleic acid, glycolic acid, malonic acid, methanesulfonic acid, formicacid, malic acid, gluconic acid, alanine, glycin, lactic acid,hydroxyethylidene diphosphonic acid, nitrilotris(methylene phosphonicacid), or phosphonobutane tricarboxylic acid.
 12. (canceled) 13.(canceled)
 14. (canceled)
 15. (canceled)
 16. (canceled)
 17. A method forpolishing a glass substrate, the method comprising: preparing apolishing composition comprising silicon dioxide, an acid, and water;and polishing the surface of a glass substrate, using the preparedpolishing composition.
 18. The method for polishing a glass substrateaccording to claim 17, wherein said polishing the surface of a glasssubstrate comprises: preliminarily polishing the surface of the glasssubstrate; and finish-polishing the surface of the preliminarilypolished glass substrate, in which the polishing composition is used inthe finish-polishing of the surface of the preliminarily polished glasssubstrate.
 19. The method for polishing a glass substrate according toclaim 17, wherein said preparing a polishing composition comprisesdiluting the polishing composition with water.
 20. The method forpolishing a glass substrate according to claim 19, wherein the volume ofwater to be used for dilution of the polishing composition is not morethan 50 times as large as the volume of the polishing composition beforedilution.
 21. The method according to claim 1, wherein the acid is atleast one selected from the group consisting of phosphoric acid,pphosphonic acid, phosphinic acid, acetic acid, itaconic acid,methanesulfonic acid, formic acid, hydroxyethylidene diphosphonic acid,nitrilotris (methylene phosphonic acid), and phosphonobutanetricarboxylic acid.